Supporting finger for annealing furnaces



Jan.- .29,929. I

'F. A. 'FAHRENWALD", 'suP-P RTING FINGER. FOR "-ANNEALING-I FURNACESFiled A ril 20, 1928 so made.

atented Jan. 29, 1929.

STATES FRANK A; FAHRENWALD, OF CHICAGO, ILLINOIS.

SUPPORTING FINGER FOR ANNEALING- FURNACES.

Application med April 20, 1928. Serial No. 271,451.

This invention relates to furnaces employed for heating sheets or otherobjects that have to be supported above the hearth of the furnace duringthe heating operation,

x and particularly to a novel construction of upstanding support in theform of a finger, a plurality of which at suitably spaced intervals arepresented within the furnace chamber by endless chain carriers travelingin slotted conduits which are constructed in the hearth.

It has long been the practice to arrange a suitable number ofendlesslink carriers in position to travel through slotted conduitsincorporated in the hearth structure, and to provide thesecarriers withupstanding fingers that afford support to the sheet or other object atsuitably spaced intervals. But these fingers, under the severe stressesset up in them by unequal heating and cooling as they pass from outsideatmosphere into the furnace andfrom the furnaceback to the atmosphere,are subject to cracking, spalling, and distortion which makes themcomparatively short lived and involves considerable expense in removingthe spent fingers and introducing new ones into the links of the chains,not to mention the shutting down of the furnace while the replacement isbeing The object of the present invention is to provide a constructionof finger for the purpose stated, which will enable the finger towithstand the aforesaid temperature influences; and the invention isbased upon the discovery that the failure of fingers heretofore used isdue to the 'more rapid changes in the exterior portions of the fingerthan the interior portion thereof, so that the interior portion becomesa resistance or fulcrum against which the exterior portion must drag inexpanding and contracting, and this sets up surface stresses ofsufiicient tension totear the metal asunder and thus gradually renderthe finger useless. Accordingly, the invention proceeds upon theprinciple of giving to the finger a frame-like construction of such formthat it will have an open interior throughout the portion whichencounters serious heat effects and receive its essential strength fromspaced vertical legs of sufficiently reduced transverse section toenable the entire section of each leg to act more nearly asa unit inexpanding and contracting under changes of temperature, and which willbe sufliciently spaced apart in their union, with the body orbaseportion of the finger, as well as the supporting seat which isprovided by the upper end of the finger, that each will sustain theother transversely without causing a drag or resistance to its expansionor contraction, so that even if they should not expand and contract inunison, and one leg should expand or contract relativelyto the other,the other leg can yield transversely within its elastic limit and thetwo legs thus become mutually compensating.

In the accompanying drawing, in which the preferred and a modifiedconstruction of the invention are shown by way of illustration,

igure 1 is a conventional representation, in vertical transversesection, of a heating furnace suitable for annealing metal sheets and inwhich are installed endless conveyors provided with fingers constructedin accord-v ance with the present invention.

Figures 2 and 3 are, respectively, a side elevation and a top plan viewof a section of one of the conveyors employed in Figure 1, drawn on anenlarged scale; and

Figure 4 is a detail view representing in side elevation a finger ofslightly different construction from that shown in Figure 2.

A represents a furnace of conventional construction, having a hearth B,and C represents a series of endless chain conveyors traveling inconduits D embodied in the structure of the hearth and communicatingwith the furnace chamber through transversing slots E that permit thepassage of upstanding supporting fingers 1 carried by the endlesschains.

According to one embodiment of the pres ent invention as shown in Figure2, each finger 1 while inserted in the socket 2 of the carrying chain Cand-there secured by any suitable means, such as rivets 4, in accordancewith known practice is constructed, particularly inits upper portionwhich is subjected to severe heat, of upstanding spaced legs 5, such,for instance, as would be left by forming a longitudinally extendingtransverse opening 6 through the Finger 1, and a yoke 7 uniting theupper ends of the legs 5 and constituting the seat upon which theworkpiece rests while in support upon the conveyors. Legs 5 willpreferably be integral 'with the body 1 of the finger, as well as withthe yoke 7.

, As shown in Figure 4, a finger may consist of the body 1 secured insocket 2 by means of rivet 3 and constructed with upstanding legs 5*-that are united not onlyat their upper or 5 and the cooling influence ofthe opening 6 or 6 are such that expansion and contraction will proceedwith such correspondence in the two legs-that each will not only expandencounterat any one time,

and contract as a whole section, but neither will impose anyseriousresistance tothe expansion or contraction of the other, first, be-

cause there will be little difference in the heating and coolinginfluences which they and, secondly, because if either should expand orcontract relatively to the other,.the other can flex Within its elasticlimit transversely and thereby compensatethe temporary diiference inlongitudinal dimension.

I claim: y I 1. A finger for supporting conveyors of heating furnaces,comprising an upstanding member of frame-like construction embodying inthat portion of the finger which is subected to excessive temperaturechanges, vertical legs with intervening cooling space.

2. A finger for supporting conveyors of heating furnaces, comprising anupstanding member of frame-like construction embodying in that portionof the finger'which is subjected to excessivetemperature changes,

vertical legs with intervening cooling'space; said legs being unitedattop by a seat for the workpiece that is to be supported.

3. A finger for supporting carriers'of heating furnaces, consisting of amember adapted to be mounted upon the carrier in upstandjing positionand comprising a body portion,

a seat-forming arch, and upstanding legs with a cooling space betweenthem; said legs ,being integrally united above and below by said archand said body portion.

4. A finger for supporting carriers of heatin furnaces, consisting of amember adapted lto ioemounted upon the carrier in upstanding positionand comprising a body-portion, a seat-forming arch, 'and upstanding legswith a cooling space between them; said legs being integrally unitedaboveand below by said arch and said body portion, and intermediatelyconnected by a bridging member which divides the cooling space betweenthem. Signed at Chicago, Illinois, this 6th day of April, 1928. I

FRANK A. FAHRENWALD.

